Carrier's Carrier - 3Com S7906E Configuration Manual

Figure 1-9 Network diagram for inter-provider VPN option C
To improve the scalability, you can specify an RR in each AS, making it maintain all VPN-IPv4 routes
and exchange VPN-IPv4 routes with PEs in the AS. The RRs in two ASs establish an inter-provider
VPNv4 connection to advertise VPN-IPv4 routes, as shown in Figure 1-10.
Figure 1-10 Network diagram for inter-provider VPN option C using RRs

Carrier's Carrier

Introduction to carrier's carrier
It is possible that a customer of the MPLS L3VPN service provider is also a service provider. In this case,
the MPLS L3VPN service provider is called the provider carrier or the Level 1 carrier, while the customer
is called the customer carrier or the Level 2 carrier. This networking model is referred to as carrier's
carrier. In this model, the Level 2 service provider serves as a CE of the Level 1 service provider.
For good scalability, the Level 1 carrier does not inject the external routes of a Level 2 carrier; it only
injects routes for switching packets from different sites of the Level 2 carrier. The external routes
maintained by a Level 2 carrier are exchanged through BGP sessions established between related
1-12